FIG. 1 is a drawing illustrating an LCD back light circuit of an electric refrigerator in accordance with a conventional art.
As shown in FIG. 1, the LCD back light circuit includes a microcomputer 100 for controlling an ON/OFF operation of a circuit and a back light unit 110 connected between a port terminal of a microcomputer and a ground and turned on/off under the control of the microcomputer.
The back light unit 110 includes a light emitting diode group 110-1 in which a plurality of light emitting diodes are serially connected in a forward direction, and a resistance R1 serially connected to the light emitting diode group 110-1 and distributing a power source voltage.
There are provided a plurality of light emitting diode groups which are connected in parallel between the port terminal and the ground.
The operation of the LCD back light circuit of an electric refrigerator in accordance with the conventional art will now be described in detail.
When power is applied to the back light unit 110 through the port terminal of the microcomputer 100, a current of the power source is equally distributed to a plurality of nodes and turns on the light emitting diode groups 110-1, 110-2, . . . , 110-M, and flows to the ground through the resistances R1, R2, . . . , RM. A voltage of the power source is distributed at a certain rate by the light emitting diode groups 110-1, 110-2, . . . , 110-M and the resistances R1, R2, . . . , RM.
However, the LCD back light circuit of an electric refrigerator in accordance with the conventional art has the following problem.
That is, if the port terminal connected to the microcomputer 100 is short, the entire back light unit 110 is turned off.
In addition, if one of light emitting diodes of the LCD back light circuit is defective, the normal light emitting diodes serially connected to the defective light emitting diode are simultaneously turned off, causing a problem that luminance of the LCD is not uniform.